YPCLNT(3) BSD Library Functions Manual YPCLNT(3)NAME
yp_all, yp_bind, yp_first, yp_get_default_domain, yp_master, yp_match, yp_next, yp_order,
yp_unbind, yperr_string, ypprot_err -- Interface to the YP subsystem
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <rpc/rpc.h>
#include <rpcsvc/ypclnt.h>
#include <rpcsvc/yp_prot.h>
int
yp_all(const char *indomain, const char *inmap, struct ypall_callback *incallback);
int
yp_bind(const char *dom);
int
yp_first(const char *indomain, const char *inmap, char **outkey, int *outkeylen,
char **outval, int *outvallen);
int
yp_get_default_domain(char **outdomain);
int
yp_master(const char *indomain, const char *inmap, char **outname);
int
yp_match(const char *indomain, const char *inmap, const char *inkey, int inkeylen,
char **outval, int *outvallen);
int
yp_next(const char *indomain, const char *inmap, const char *inkey, int inkeylen,
char **outkey, int *outkeylen, char **outval, int *outvallen);
int
yp_order(const char *indomain, const char *inmap, int *outorder);
void
yp_unbind(const char *dom);
char *
yperr_string(int incode);
int
ypprot_err(unsigned int incode);
DESCRIPTION
The ypclnt suite provides an interface to the YP subsystem. For a general description of
the YP subsystem, see yp(8).
For all functions, input values begin with in and output values begin with out.
Any output values of type char ** should be the addresses of uninitialized character point-
ers. These values will be reset to the null pointer (unless the address itself is the null
pointer, in which case the error YPERR_BADARGS will be returned). If necessary, memory will
be allocated by the YP client routines using malloc(), and the result will be stored in the
appropriate output value. If the invocation of a YP client routine doesn't return an error,
and an output value is not the null pointer, then this memory should be freed by the user
when there is no additional need for the data stored there. For outkey and outval, two
extra bytes of memory are allocated for a '\n' and '\0', which are not reflected in the val-
ues of outkeylen or outvallen.
All occurrences of indomain and inmap must be non-null, NUL-terminated strings. All input
strings which also have a corresponding length parameter cannot be the null pointer unless
the corresponding length value is zero. Such strings need not be NUL-terminated.
All YP lookup calls (the functions yp_all(), yp_first(), yp_master(), yp_match(), yp_next(),
yp_order()) require a YP domain name and a YP map name. The default domain name may be
obtained by calling yp_get_default_domain(), and should thus be used before all other YP
calls in a client program. The value it places outdomain is suitable for use as the
indomain parameter to all subsequent YP calls.
In order for YP lookup calls to succeed, the client process must be bound to a YP server
process. The client process need not explicitly bind to the server, as it happens automati-
cally whenever a lookup occurs. The function yp_bind() is provided for a backup strategy,
e.g. a local file, when a YP server process is not available. Each binding uses one socket
descriptor on the client process, which may be explicitly freed using yp_unbind(), which
frees all per-process and per-node resources to bind the domain and marks the domain
unbound.
If, during a YP lookup, an RPC failure occurs, the domain used in the lookup is automati-
cally marked unbound and the ypclnt layer retries the lookup as long as ypbind(8) is running
and either the client process cannot bind to a server for the domain specified in the
lookup, or RPC requests to the YP server process fail. If an error is not RPC-related, one
of the YP error codes described below is returned and control given back to the user code.
The ypclnt suite provides the following functionality:
yp_match() Provides the value associated with the given key.
yp_first() Provides the first key-value pair from the given map in the named domain.
yp_next() Provides the next key-value pair in the given map. To obtain the second pair,
the inkey value should be the outkey value provided by the initial call to
yp_first(). In the general case, the next key-value pair may be obtained by
using the outkey value from the previous call to yp_next() as the value for
inkey.
Of course, the notions of ``first'' and ``next'' are particular to the type of
YP map being accessed, and thus there is no guarantee of lexical order. The
only guarantees provided with yp_first() and yp_next(), providing that the
same map on the same server is polled repeatedly until yp_next() returns
YPERR_NOMORE, are that all key-value pairs in that map will be accessed
exactly once, and if the entire procedure is repeated, the order will be the
same.
If the server is heavily loaded or the server fails for some reason, the
domain being used may become unbound. If this happens, and the client process
re-binds, the retrieval rules will break: some entries may be seen twice, and
others not at all. For this reason, the function yp_all() provides a better
solution for reading all of the entries in a particular map.
yp_all() This function provides a way to transfer an entire map from the server to the
client process with a single request. This transfer uses TCP, unlike all
other functions in the ypclnt suite, which use UDP. The entire transaction
occurs in a single RPC request-response. The third argument to this function
provides a way to supply the name of a function to process each key-value pair
in the map. yp_all() returns after the entire transaction is complete, or the
foreach function decides that it does not want any more key-value pairs. The
third argument to yp_all() is:
struct ypall_callback *incallback {
int (*foreach)();
char *data;
};
The char *data argument is an opaque pointer for use by the callback function.
The foreach function should return non-zero when it no longer wishes to
process key-value pairs, at which time yp_all() returns a value of 0, and is
called with the following arguments:
int foreach (
int instatus,
char *inkey,
int inkeylen,
char *inval,
int invallen,
char *indata
);
Where:
instatus Holds one of the return status values described in
<rpcsvc/yp_prot.h>: see ypprot_err() below for a function that
will translate YP protocol errors into a ypclnt layer error code
as described in <rpcsvc/ypclnt.h>.
inkey, inval The key and value arguments are somewhat different here than
described above. In this case, the memory pointed to by inkey
and inval is private to yp_all(), and is overwritten with each
subsequent key-value pair, thus the foreach function should do
something useful with the contents of that memory during each
iteration. If the key-value pairs are not terminated with
either '\n' or '\0' in the map, then they will not be terminated
as such when given to the foreach function, either.
indata This is the contents of the incallback->data element of the
callback structure. It is provided as a means to share state
between the foreach function and the user code. Its use is com-
pletely optional: cast it to something useful or simply ignore
it.
yp_order() Returns the order number for a map.
yp_master() Returns the hostname for the machine on which the master YP server process for
a map is running.
yperr_string()
Returns a pointer to a NUL-terminated error string that does not contain a '.'
or '\n'.
ypprot_err() Converts a YP protocol error code to a ypclnt error code suitable for
yperr_string().
RETURN VALUES
All functions in the ypclnt suite which are of type int return 0 upon success or one of the
following error codes upon failure:
[YPERR_BADARGS] The passed arguments to the function are invalid.
[YPERR_BADDB] The YP map that was polled is defective.
[YPERR_DOMAIN] Client process cannot bind to server on this YP domain.
[YPERR_KEY] The key passed does not exist.
[YPERR_MAP] There is no such map in the server's domain.
[YPERR_DOM] The local YP domain is not set.
[YPERR_NOMORE] There are no more records in the queried map.
[YPERR_PMAP] Cannot communicate with portmapper (see rpcbind(8)).
[YPERR_RESRC] A resource allocation failure occurred.
[YPERR_RPC] An RPC failure has occurred. The domain has been marked unbound.
[YPERR_VERS] Client/server version mismatch. If the server is running version 1 of the
YP protocol, yp_all() functionality does not exist.
[YPERR_BIND] Cannot communicate with ypbind(8).
[YPERR_YPERR] An internal server or client error has occurred.
[YPERR_YPSERV] The client cannot communicate with the YP server process.
SEE ALSOmalloc(3), yp(8), ypbind(8), ypserv(8)AUTHORS
Theo De Raadt
BSD May 21, 1997 BSD